21155123 has 32 divisors (see below), whose sum is σ = 26127360. Its totient is φ = 16898560.

The previous prime is 21155119. The next prime is 21155131. The reversal of 21155123 is 32155112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21155123 - 2² = 21155119 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21155095 and 21155104.

It is not an unprimeable number, because it can be changed into a prime (21155723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 254840 + ... + 254922.

It is an arithmetic number, because the mean of its divisors is an integer number (816480).

Almost surely, 2^21155123 is an apocalyptic number.

21155123 is a deficient number, since it is larger than the sum of its proper divisors (4972237).

21155123 is a wasteful number, since it uses less digits than its factorization.

21155123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187.

The product of its digits is 300, while the sum is 20.

The square root of 21155123 is about 4599.4698607557. The cubic root of 21155123 is about 276.5700733751.

The spelling of 21155123 in words is "twenty-one million, one hundred fifty-five thousand, one hundred twenty-three".